In drive units of this type, both the displacing motion and the rotating motion of the vertical slats are driven by means of the shared driving element. In the meaning of this patent application differential gear is defined here such that a driving element with two driven elements is coupled using gears, so that either both driven elements or, with one driven element fixed, the other driven element are or is driven by means of the driving element. Moreover, by means of a differential gear of this type, it is possible, like in a differential, by fixing one driven element, to achieve a reversal of direction of the other driven element. In drive units of the above-mentioned type, a driving gear for the displacing of the vertical slats is driven, for example, by means of a planet gear as a differential gear. In this case, moreover, a spline shaft for the rotation of the slats is driven via an outer ring on the pinion cage of the planet gear. Since the necessary forces for the rotation of the slats are lower than for the displacing of the slats, when the driving element is actuated, first the necessary rotating motion of the vertical slats is carried out and then the displacing of the vertical slats. In particular, in case of an open vertical Venetian blind, at first the vertical slats are rotated into their closed orientation and then extended in this closed, rotated position for closing the vertical Venetian blind. To open the vertical Venetian blind, the shared driving element is actuated in the opposite direction. Here, the vertical slats again rotate at first into their opposite rotated position because of the lower force that is needed for this. When this opposite rotated position is reached, a stop limits a first rotation, such that the rotating motion and the related first driven element are blocked. With another actuation of the shared driving element, a displacement of the vertical slats takes place by means of the second driven element for the complete opening of the vertical Venetian blind. So that the vertical slats do not now get hooked up in their opposite rotated position with the opening of the vertical Venetian blind, this opposite rotated position is aligned in such a way that complete shading in this opposite rotated position is not possible. However, with different angles of incidence, it would be desirable for the vertical slats to be able to be closed completely in both directions of rotation. Up to now, however, this possibility requires either a separate driving element for the rotating motion or a gear with switching possibilities between rotating motion and displacing motion. A separate driving element for the rotating motion is uncomfortable, since in this case, for example, two ball chains have to be operated and, according to experience, the wrong ball chain is usually actuated. Thus, instead of performing a turning of the vertical slats, a displacing of the slats may be actuated in this case, which, in the closed rotated state, may lead to hooking up of the vertical slats. A switchable gear is in turn complicated and prone to difficulties. Moreover, the actuation of such a switchable gear is possible only with difficulty at unfavorable pulling angles.